1. Field of the Invention
The present invention relates to wireless communication system protocols. More particularly the present invention relates to encoding and decoding connection payload information in a Medium Access Control (MAC) Protocol Data Unit (PDU).
2. Description of the Related Art
Broadband wireless networks are based on various communication standards, for example, the Institute of Electrical and Electronics Engineers (IEEE) 802.16e based Worldwide Interoperability for Microwave Access (WiMAX) standard, and its evolution to IEEE 802.16m, provides various types of services such as voice, packet data exchange, and the like. In such a network, user data is exchanged between a subscriber station and a base station by establishing a connection. Multiple connections exist between the subscriber station and the base station to carry the user data belonging to multiple applications. The user data, in the form of connection payload, goes through various layers of protocol architecture of a communication system.
The IEEE 802.16m communication standard is associated with a protocol architecture that includes Physical (PHY) and Medium Access Control (MAC) layer specifications. The MAC layer comprises three sub-layers which are the specific Convergence Sub-layer (CS), the MAC Common Part Sub-layer (MAC CPS), and the security sub-layer. The CS provides transformation and/or mapping of external network data, received through the CS Service Access Point (SAP), into MAC Service Data Units (SDUs) received by the MAC CPS through the MAC SAP. This includes classifying external network SDUs and associating the external network SDUs to an appropriate MAC connection. It may also include other functions such as Payload Header Suppression (PHS).
The MAC CPS receives data from the various CSs, through the MAC SAP, classified to particular MAC connections. Data is transferred between the MAC CPS and the PHY layer via the PHY SAP. The MAC CPS also contains a separate security sub-layer that provides authentication, secure key exchange, and encryption. The MAC CPS forms an IEEE 802.16m based MAC PDU. The MAC PDU format includes a Generic MAC Header (GMH), an Extended Header (EH), and payload. Each connection payload includes one or more MAC SDUs or MAC SDU fragments received from the CS layer for the particular connection.
Further, the GMH format (based on the IEEE 802.16m standard) includes a Flow Identifier (Flow ID) field, an Extended Header (EH) field, and a Length field. A connection is identified by the Flow ID field. The EH field indicates whether an extended header is present in the MAC PDU or not. Further, the Length field gives information about the MAC PDU payload. The EH field includes a subfield to identify the type of specific contents. The EH field contains a type field and a body contents field. The type field indicates the type of extended header and the body contents field indicates the type-dependent contents.
The MAC PDU format includes a fixed size GMH, an optional EH, and payload. Thus, during communication each application will be associated with one connection. Hence, the connection information will be stored in the MAC PDU. As each connection is associated with a Flow ID, the Flow ID will be stored in the GMH and in-band signaling information will be accommodated in the EH. Further, the payload information will be stored in a payload field.
Currently, the MAC PDU is capable of accommodating information associated with one connection at a time. However, there may be a case that information associated with more than one connection needs to be sent using the same MAC PDU format to increase the efficiency of the communication and for enabling backward compatibility of the communication standards.
Hence there exists a need to manage multiple connection information in the MAC PDU.